1. The mechanism of adrenocorticotrophic hormone (ACTH)-induced hypertension in the sheep has been examined.
2. Hypertension was dependent on the presence of the adrenal gland.
3. ACTH-hypertension was not reproduced by administration of cortisol, corticosterone, deoxycorticosterone or deoxycortisol, alone or in combination.
4. Intact adrenal nerves were not necessary for the hypertension.
5. It is postulated that an adrenal factor other than those studied may be responsible for the hypertension.